LiquidJS is a Shopify/GitHub Pages compatible template engine written in pure JavaScript. In versions 10.25.7 and below, the date filters strftime implementation parses width specifiers like %9999999d and forwards the captured width unchecked into pad()/padStart(), leading to memory and render limit bypass. In src/util/underscore.ts, the pad loop performs unbounded string concatenation without consulting the Contexts memoryLimit or renderLimit, so a single small template ({{ x | date: %5000000d }}) produces megabytes of output and unbounded CPU. The memoryLimit and renderLimit options the docs (src/liquid-options.ts:87-92) advertise as DoS controls — and which the docstring explicitly mentions for strftime — are entirely bypassed. Exploitation can cause large memory allocations, high CPU usage, or OOM crashes per render. This issue has been fixed in version 10.26.0.
Weakness
The product does not properly control the allocation and maintenance of a limited resource.
Potential Mitigations
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/147.html
- https://cwe.mitre.org/data/definitions/227.html
- https://cwe.mitre.org/data/definitions/492.html